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Theta-burst stimulation (TBS), a frequently used paradigm of repetitive Transcranial Magnetic Stimulation (rTMS), is a powerful neuromodulation technique that can induce long-lasting plastic changes in neural activity. However, results in patients and healthy volunteers are highly variable since knowledge of TBS at the neural level is still incomplete. Recently, Romero et al. (in preparation) reported that continuous TBS (cTBS; 50 Hz triplets repeated every 200 ms for 20 s) reduces cortical excitability in the macaque parietal cortex, which did not recover for at least two hours. Furthermore, in a smaller fraction of the recorded neurons, the authors found reduced task-related activity after cTBS. These results open a window to study how these neuronal changes affect behaviour. Here, we studied the effect of cTBS over parietal cortex (area PFG) by measuring the grasping times (GT) and reaction times (RT) during a visually-guided grasping (VGG) task. First, two rhesus monkeys were trained to perform the VGG under six different conditions, combining the grasping of two objects (large and small cylinder, i.e. power grip and pad-to-side grip, respectively) with three different stimulations: no-stimulation (NS), low-stimulation (LS-cTBS; 40% of the resting motor threshold -rMT-), and high-stimulation (HS-cTBS; 80% of the rMT), applied with the TMS coil oriented at a 45-degree angle. In an additional experiment, we repeated the same conditions in one monkey with cTBS applied at 30-degree. Interestingly, we observed differential effects on the GTs (depending on stimulation intensity, grip type and coil-angle) with long-term effects for up to two hours. HS-cTBS applied at 45-degree significantly prolonged GTs for the large object (p<0.01), while GTs were reduced for the small object (p<0.01). In contrast, LS-cTBS decreased GTs for the large object (p<0.01) and increased GTs for the small object (p<0.01). In this control experiment, cTBS applied at 30 degrees reversed the behavioural effects for all HS-cTBS and LS-cTBS conditions. RTs were highly variable and no consistent cTBS effect was observed. These experimental results confirm the high variability and spatial specificity of cTBS, and demonstrate long-lasting effects of cTBS on GT (which are in line with the collected neuronal data). Further combined electrophysiological and behavioural studies are required to systematically study the effects of different intensities of cTBS, which can be valuable to refine the existing therapeutic protocols.